Roman Numerals for kids
Discussion
So.. we did Gambler's Fallacy a while back. Now it's Roman numerals. My lad (now 9) has a thirst for learning, long may it continue.
He was asking me to give him a number and he'd write it in Roman numerals. I have no idea (apart from the easy ones), so was using google to check his answers. I gave him 99 and he wrote IC (one less than 100). The correct answer was XCIX (ten less than 109). You can't have one less than anything ten times its own value.
Tonight he wanted a few more and I was firing random numbers in the thousands to him and he was getting them pretty much spot-on. That was until I asked him 1945. In words he would have written five less than 1950. Only the answer is 10 less than 1955 (MCMXLV). You can have one less than 10, 10 less than a hundred and so on, but not 5 (or 50 or 500) less than anything.
He's got his head round the principle, but does anyone know the logic behind this so I can try and explain why?
He was asking me to give him a number and he'd write it in Roman numerals. I have no idea (apart from the easy ones), so was using google to check his answers. I gave him 99 and he wrote IC (one less than 100). The correct answer was XCIX (ten less than 109). You can't have one less than anything ten times its own value.
Tonight he wanted a few more and I was firing random numbers in the thousands to him and he was getting them pretty much spot-on. That was until I asked him 1945. In words he would have written five less than 1950. Only the answer is 10 less than 1955 (MCMXLV). You can have one less than 10, 10 less than a hundred and so on, but not 5 (or 50 or 500) less than anything.
He's got his head round the principle, but does anyone know the logic behind this so I can try and explain why?
HQ2 said:
So.. we did Gambler's Fallacy a while back. Now it's Roman numerals. My lad (now 9) has a thirst for learning, long may it continue.
He was asking me to give him a number and he'd write it in Roman numerals. I have no idea (apart from the easy ones), so was using google to check his answers. I gave him 99 and he wrote IC (one less than 100). The correct answer was XCIX (ten less than 109). You can't have one less than anything ten times its own value.
Tonight he wanted a few more and I was firing random numbers in the thousands to him and he was getting them pretty much spot-on. That was until I asked him 1945. In words he would have written five less than 1950. Only the answer is 10 less than 1955 (MCMXLV). You can have one less than 10, 10 less than a hundred and so on, but not 5 (or 50 or 500) less than anything.
He's got his head round the principle, but does anyone know the logic behind this so I can try and explain why?
Roman numerals are crazy. You're right about only being able to subtract decimal units, 1,10,100, but not 50 or 5. They did that so that in years to come immature schoolboys couldn't giggle at 495 being VD. He was asking me to give him a number and he'd write it in Roman numerals. I have no idea (apart from the easy ones), so was using google to check his answers. I gave him 99 and he wrote IC (one less than 100). The correct answer was XCIX (ten less than 109). You can't have one less than anything ten times its own value.
Tonight he wanted a few more and I was firing random numbers in the thousands to him and he was getting them pretty much spot-on. That was until I asked him 1945. In words he would have written five less than 1950. Only the answer is 10 less than 1955 (MCMXLV). You can have one less than 10, 10 less than a hundred and so on, but not 5 (or 50 or 500) less than anything.
He's got his head round the principle, but does anyone know the logic behind this so I can try and explain why?
The other rule I learnt is that you can't repeat the same letter more than 3 times. So 80 is LXXX but 90 isn't LXXXX. It's XC. But you look at many clocks, and 4 will be shown as IIII instead of IV. Go figure.
The big issue with them is trying to do maths. There's no zero, which completely screws you.
You've pretty much figured it out already from first principles.
Theoretically, the biggest number you can write in Roman numerals is 3999
MMMCMXCIX
MMM CM XC IX
3000+900+90+9
or (1000+1000+1000) + (1000-100) + (100-10) + (10-1)
Anyone want to hang around for 1985 years to see how we count then?
The use of IIII for 4 on clocks is to make it look more symmetrical. On a clock face you have (from the top down):
XII (12)
XI and I (11 and 1)
X and II (10 and 2)
IX and III (9 and 3)
VIII and IIII (8 and a cheat's 4)
VII and V (7 and 5)
VI (6)
So you can see it makes one bit of the clock very slightly tidier looking!
Theoretically, the biggest number you can write in Roman numerals is 3999
MMMCMXCIX
MMM CM XC IX
3000+900+90+9
or (1000+1000+1000) + (1000-100) + (100-10) + (10-1)
Anyone want to hang around for 1985 years to see how we count then?
The use of IIII for 4 on clocks is to make it look more symmetrical. On a clock face you have (from the top down):
XII (12)
XI and I (11 and 1)
X and II (10 and 2)
IX and III (9 and 3)
VIII and IIII (8 and a cheat's 4)
VII and V (7 and 5)
VI (6)
So you can see it makes one bit of the clock very slightly tidier looking!
marshalla said:
I'd read XCIX as 90+9 (or (100-10)+(10-1)), not 109-10.
Ten less than 100 plus one less than 10 - I suppose is easier than ten less than 109. Slartifartfast said:
1945 = M, CM, XL, V. 1000, 900, 40, 5
Correct of course, but both examples accept you take 10 from a larger number then add the extra. To the enquiring mind of a nine year old why should 45 be ten less than fifty plus five, when "taking 5 from 50 would be so much easier". He has his head around it, just wants to know why! Edited by HQ2 on Thursday 19th March 22:54
TwigtheWonderkid said:
marshalla said:
TwigtheWonderkid said:
But you look at many clocks, and 4 will be shown as IIII instead of IV.
No ancient Roman clock uses IIII.A quick google suggests that it is one theory, but there are plenty of others and no-one really knows...
HQ2 said:
Correct of course, but both examples accept you take 10 from a larger number then add the extra. To the enquiring mind of a nine year old why should 45 be ten less than fifty plus five, when "taking 5 from 50 would be so much easier". He has his head around it, just wants to know why!
Probably because the rule was invented before the shorthand for five and fifty.Edited by HQ2 on Thursday 19th March 22:54
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